( :^<>^ ) 



But ill coiKsequejice of the special position of the lines d, the locus 

 (/-*) now consists of the three hyperboloids iji^ (i^d^ a^, {d^d^ ci^ (li) 



J 8. Two triplets of planes «j, «,> «3 ^"d 1^1, /ij' .^3 determine a 

 }1encil of cubic surfaces of which the nine lines («/.•/?() form the 

 tjasis. If these surfaces are conjugated })rojectivel3' to the planes 

 through an arbitrary line /, the surface 0\ generated by the two 

 jjencils contains besides the already mentioned ten lines six lines 

 inore of wliich each of the given six planes furnishes one. 



These sirU'tni lines form a configuration, in which each line is 

 intersected by six others; it is identical to the figure which is 

 generated when four arbitrary planes w. are intersected b}' four 

 other planes /?/,:. For, the planes through /, conjugated to the fignres 

 {;u^,a.^,<'.„) and (i'?i,|l,, /^j) can be called successively /-^^ and a^. 



! Let t be a transversal of the lines /, («, /^J, («^ ^J, («, /ij. The 

 projectivit_y indicated above can be arranged in such a way that 

 (he plane (It) is conjugated to the cubic surface passing through a 

 |)oint of t, hence containing t. In an analogous manner we can deal 

 jvith two other lines, each of which rests on / and on three not 

 intersecting lines {ati^i). Then the projectivity is determined and 

 the surface O^ generated in this way evidentl}^ now contains 

 nineteen lines. 



We finally note that E. Traynai^d {BuU.Soc. Mat. de France, vol. 

 38, p. 280) has described an (>' with thirty lines. 



Chemistry. — ''The application of the neiv tJieory of aUoiropy 

 to the .system sulphur.'' By Prof. A. Smits. (Communicated by 

 Prof. A. F. Holleman). 



Those who have been occupied with the sulphur problem up to 

 now, have always thought the pseudo system to be binary, i.e. they 

 assumed that they had to deal with two pseudo components or two 

 kinds of molecules, which can be converted into each other, and 

 one of which gives rise to the formation of the well-kno\vn crystallized 

 modification, the monoclinic and the rhombic sulphur, whereas the 

 other would |)roduce the amorphous sulphur, called so because attempts 

 to make this form of sulphur crystallize have not been successful 

 as yet. 



Though in my opinion the above view is not the correct one, 1 will 

 begin willi treating sulphur as a pseudo-binary system, and show 



